The overall objective of this project is to provide information about the molecular structure of biologically important compounds. Specifically, we hope to assist in the elucidation of the action of Vitamin B12 coenzyme by studying model compounds. These cobaloxime compounds contain cobalt surrounded by ligands which provide an environment for cobalt that is chemically similar to that in B12 coenzyme. The accurate structure determinations of the proposed series of molecules is expected to show the change in binding (Co-N bond length) of one axial ligand when the opposite axial ligand is varied. An x-ray structure analysis will be started on Chalaropsis lysozyme if suitable crystals become available. The methods used are primarily those of single crystal x-ray diffraction using a computer controlled diffractometer with control programs coded, in part, at Vanderbilt. Emphasis is on results of high precision.